Full-field internal 3D deformations measurement of transparent soil using 3D-DIC combined with optical slicing

Digital image correlation (DIC) and particle image velocity (PIV) are highly effective non-contact methods to accurately measure full-field deformations in transparent soil model testing (TSMT). The nature of transparent soils combined with the rapid development of three-dimensional (3D) DIC/PIV techniques means that the acquisition of the full internal 3D deformations is now technically feasible. However, current approaches focus on two-dimensional (2D) in-plane displacements and typically ignore out-of-plane displacements. This paper presents an approach of combining 3D-DIC with optical slicing to observe 3D movements of transparent soil using custom MATLAB programming. A rigid body motion (RBM) test of a transparent soil sample is first conducted to estimate the accuracy of the proposed algorithm. A vertically loaded circular footing test is subsequently performed as a proof of concept; multiple-slice images of the soil are captured using a new experimental apparatus and processed by the 3D-DIC algorithm, and the resultant 3D displacements of all slices are reconstructed to visualize the soil deformations in 3D space. The findings confirm that the proposed 3D-DIC algorithm is accurate and the optical slicing with supplementary spatial reconstruction method enables visualization of transparent soil in 3D space, which can be used in future TSMT.